Grinding mill



Nqv. 10, 1931. H. HARDINGE GRINDING MILL Filed Aug. 30, 1929 2 Sheets-Sheet l kD v- Patented ov. 1.0, `1931 UNITED STATES PATENT OFFICE HARLOWE HARDINGE, 0F YORK, PENNSYLVANIA, .ASSIGNOIR T0 HARDINGE COMPANY, INCORPORATED, OF YORK, PENNSYLVANIA, A CORPORATION OF NEW YORK @BINDING MILL This invention relates to grinding mills, and more particularly to means for controlling the operating characteristics of a grinding mill having inlet and outlet openings at one end for permitting elastic iiuid to enter and leave the mill. l

Among the objects of the invention is to provide means whereby currents of air or of other elastic iuid introduced into a grinding mill may be varied'in their course within the mill to suit existing grinding conditions and to enable the production of a uniform prod-t uct of a desired ineness. i

Another object of the invention is to provide means for enabling regulation of the neness and quantity of ground material removed from a grinding mill by fluid-dotation.

Otherobjects and advantages of the invention will be pointed out hereinafter in the description and rclaims and illustrated in the drawings, in which:

Fig. 1 is a section of a conical mill diagrammatically illustrating effects produced by means of the present invention. E

Fig. 1A is a detail illustrating how the conical deflecting means may be constructed in sections. v

Fig. 2 is a cross sectional detail of conical deflecting means adapted to replace similar means illustrated in Fig. 1.

Fig. 3 is a sectional elevation of the discharge end of a grinding mill in association with eXhauster means.

Fig. 4 is a detail taken on line 4 4 of Fig 3.

Although the invention has application to other forms of grinding mills, it is particularly suited for use in connection with the well known Hardinge conical mill in connection with which I have chosen to illustrate the prin- `ciples thereof. @ne form of the conical mill i is illustrated in Fig. 1. The drum has a cylindrical portion 10 andconical endsportions 11, 12 which are secured to trunnions 13, 14, respectively. Material is fed from the hopper 15 at the feed end of the mill through trunnion 13. As illustrated, the mill may be closed by a plate 16 at the feed end of the mill and the air currents which are used to carry Application led August 30, 1929. Serial No. 389,339.

trunnion 14 and to leave the mill through a conduit 17 centrally disposed within trunnion 14. lglate 16 is essential when the mill is to be operated under pressures other than atmospheric pressure.

When the conical mill is used with its fluid inlet and outl-et openings at one end it o erates on a reverse current principle, the uid currents entering through annular 'o ening 18 and leavingthrough conduit 17 onduit 17 is supported within trunnion 14 by means of stays 19 which are spaced peripherally about conduit 17 so as to permit'air to freely pass through the space 18. The reverse current principle by which the ground product of a mill is removed has been very satisfactory in the past, and the substance of the present invention is directed to the production of a uniformly fine product of a desired fineness. Such refinement of operatin characteristics is a feature particularly esired in mills which are used in installations in which coal is ground and directly fed to the furnaces. Without the improvements to be described hereinafter, it has been found that the fluid currents passing through a mill are` likely to occasionally pick up particles of-material larger than of the size desired as a product. For grinding ordinary materials such as clay and ores, this result offers no particular problem because it is possible to provide a classifier adapted to return the oversize material to the drum for re-grinding, but when the grinding mill is used in an installation for grinding coal it is desirable that .no oversize material be permitted to be lcarried to the burners, and that the useof special classifiers be eliminated because of the high velocity of the air passing throughE and leaving the grindby means of webs 22 which extend radially therefrom andare associated with a lining the product from the mill are caused to enter member 23. I `When the conical deecting at the discharge end of the mill through means 21 is 11.1.3116 .up vofseveral members, *10i each individual member may take the form of that illustrated in Fig. 1A, in which 21a is a portion of the conical deliecting means, 23a is a lining member and 22a is a web connecting the portion of the deiiector means 21a with the lining member 23a. The deliecting means is provided to deflect air entering the mill in a course along the inner wall of the drum so that the wall of the drum will be sweptby a fast moving current of air.

During the rotation of any mill a certain portion of the product or material inside of the mill sticks or adheres close to the lining.

This action may be reduced b providing smooth linings, but it is desira le that linings beribbed or grooved in order to prevent material within'the mill from sliding as the drum rotates, and unless some provision is made for releasin the fine material adhering close to the ining such material will not be available as a product and will also adversely affect grinding conditions. When a grinding mill is in operation, the material adhering to the linings drops across the current of air and is sucked out of the system. Some of this material has not been sufiicient ly ground to the desired lineness and it would not be removed from the mill but for the fact that it is caused to fall across the ath of a current of air leaving the mill.

n accordance with the principles of'my invention, any material clinging to the lining will drop as usual, but it will first come into contact with the current of air entering the mill and be carried by that air in a course y along the inner wall of the mill. This current of air blows the material back into the mill before it may reach the discharge current of air going in the other direction. This action is produced by the deiecting qualities of the conical delecting means 21 which is so positioned in the inlet portion of the mill to direct the incoming currents .I of air. As illustrated in Fig. 1, a particle of Cmaterial reaching the position as at 25 would be carried by the incoming current of air in a ldirection similar to that described by the broken line 26 and would follow a trajectory carrying the particle well backward into the mill. The velocity of the air in the vicinity of 25is much higher than when the article reaches a remote portion of its trajectory for in the latter position the mill is of greater volume and thevelocity of the air is reduced and, therefore, the particle is permitted to fall,without coming into contact with the high velocity air about to leave the mill through conduit 17.

The air stream developed by the conical deflecting means 21 will tend to push the grinding media and material back into the mill. This result is diagrammatically illustrated by the curve 27 identifying the lay of material within the mill under certain oper- .air in the mill is high, the material will take a position somewhat similar to that shown by the line 27 and when the velocity of the air is of less intensity the material will take a position somewhat similar to that'shown by the broken line 28. It is, therefore, apparent that a much higher load can be carried within the mill without fear of discharging the product by gravity for the air following a course as at 29 will prevent discharge of product by gravity through the space 18 and will also keep the material well out of reach of the outlet conduit 17 The use of a conical detlecting surface similar to that shown at 21 improves the operating characteristics of a conical grinding mill and enables a greater degree of lineness of product to b e produced as well as,

permitsthe use of greater velocity for the air. This is due in part to the action of the incoming air in keeping the material away lfrom the discharge end of the mill and in the outlet conduit 17. Within certain limits the higher the. velocity in the mill the liner will be the product.

It is apparent that under certain condi'- tions it might be desirable to vary the space between the conical deflecting surface and the wall of the mill in order to enable a change in the, velocity of the air passing through this space to be made without resort to a change in the speed of the exhauster. 'In Fig. 2 I have illustrated a deflecting conical surface 121 whichis connected to a lining member`123 by means of a plurality of webs 122. The space between the conical surface 121 and lining member 123 is less than the space between conical surface 21 and lining member 23 illustrated in Fig. l. In order to make corresponding members interchangeable it is only necessary that lining member 123 be similar in size and be similarly holed as lining member 23.

As illustrated in Fig. 3, it is'also possibl to vary the space between the conical deflecting surface and the Wall of the mill byv so i conduit 33. The large end of the member 32 v is provided with ay disk 34 riveted thereto and having a flange 35 engaged by bolts 36. These boltsffit into slots 37 which are sufficientl long to permit the maximum amount of adjusta-bility of member 32 longitudinally of outlet conduit 33.

v In Fig. 3 there is also shown means for controlling the quantity of material removed// from the grinding mill. Outlet conduit/33 `opens into' a box` 39 which is in communica- 'tion with the chamber 40 of an exhauster 4 1. Box 39 has an opening 42 for receiving air from conduit 33 and opening 43 for receiving air from an air supply conduit 44. ,Air supply conduit 44 isconnected with the an' inlet opening 45 of the grinding/mill 46. 47 is an adjustable damper or closure whereby it is possible to vary the area of openings 42 and 43. The single damper may be operated by sprocket 48 having engagement witha rod 49 to which the damper 41 is attachcd. The relation of closure 47 to openings 42 and 43 is such that as one of these openings is being closed the other opening'is being increased in area and vice versa. Asillustrated in Fig. 3, damper 47 is in a midposition and each of openings 4243 has approXimatelyone-half of its area obstructed. In this position someA of the air drawn through air supply conduit- 44 will by-pass the mill and be dra-wn through opening 43 into box 39 while the, quantity of air permitted to flow from the mill through outlet 33 is restricted. When closure 47 is in its lowermost position, conduit 33 will be entirely closed and all the air flowing through conduit 44 will be by-passed through opening 43 into box 39. In its highest position closure 47 will entirely close opening 43 and all of the air drawn through air supply conduit 44 will pass through the mill and be taken therefrom through outlet conduit 33.

Hopper 50 provides means by which may be removed tramp oversize material which may come out of the grinding mill during overloading conditions. As illustrated in Fig. 4, wings 51, 52 are provided for enabling adjustment of the sizeof the opening 43.

Adjustable damper 47 makes it possible to make a very positive yand -quick control ofthe output of the grinding mill and it also makes it possible to maintain a. relatively high velocity of-air through the mill to keep conditions in the mill substantially the same under all loads. Furthermore, in systems in which the grinding mill is not sealed at its feeder end. it is possible to balance the pressures within the mill by thel proper adjustment and use of damper 47.

".'What is claimed is:

l. In a grinding mill, the combination with a rotary drum having an inlet opening and having an outlet opening at one end thereof, said inlet opening surrounding said outlet opening, of delecting means in said inlet opening deiiecting fluid currents along the wall of said drum.

2. The combination set forth in claim 1 in which provision is made for permitting changes in the area between the deflecting means and the drum.

3. In a grinding mill, the combination withY conduit with the means from the drum.

tion with an outlet opeing and an inlet opening at the small end of the conical discharge portion, said inlet opening surrounding said outlet opening, of conical deliecting means 1n said inlet opening whereby elastic fluid entering the drum is caused to be directed along the inner surface of the`drum.

4. The combination set forth in claim 3 in which means are provided for permitting ad justment vof the position of the conical deflecting means relative to the drum.

5. In a grinding mill, the combination with a rotary drum having a conical discharge portion with an outlet opening and an inlet opening, said outlet opening comprising a conduit extending through the discharge end of the drum and said inlet opening comprising the space between the outlet conduit and the drum, of a conical deiiecting surface disposed in the space between the outlet conduit andthe drum but permitting elastic fluid entering the drum to pass between it and the drum.

6. In a grinding mill, the combination with a rotary drum having a conical discharge portion with an outlet opening and an inlet opening, said outlet opening comprising a conduit extending through the discharge end of the druni and said inletopening comprising the space between the outlet conduit and the drum, of eXhauste-r means having connection with said outlet conduit for causing Huid currents to pass into and out of said drum, and means including a conical deflecting surface in the inlet opening and an adjustable damper for the outlet opening for regulating the fmeness and quantity of ground material removed from the drum by fluid flotation.

7. In a grinding mill, the combination with a rotary drum having an inlet opening and having an outlet opening at one end thereof, said inlet -opening surrounding said outlet opening, of a conduit supplying fluid current to said inlet opening, means for drawing fluid through said conduit and from said drum through said outlet opening, and adjustable means controlling the quantity of Huid drawn from said drum 8. The combination set forth in claim 7 in which the adjustable means controls the size of an opening connecting the fluid supply ings, and means for simultaneously regulating the flow of the elastic fluid into the mill and the discharge of material-laden iiuid from the mill.

10. In combination, a grinding mill having outlet and inlet openings at one end, means through said outlet opening.

for drawing fluid closing the other end of the mill against the passage of fluid currents, means for causing fluid to enter into said inlet conduit and to leave the mill through said outlet conduit, and an adjustable regulating damper for controlling the amount of fluid current entering and leaving said mill, said regulating damper being operative to regulate the size of an opening through which some of the fluid current may be by-passed through the blower means without entering the mill.

11. In combination, a grinding mill having i outlet and inlet openings at one end, means closing the other end of the mill against the 4passage of fluid currents, and deflector means deflecting fluid currents entering the mill away from the outlet opening out of the mill.

12. In combination, a rotary grinding mill having outlet and inlet openings at one end, stationary inlet and outlet ducts having connection with said inlet and outlet openings, blower means for causing the flow of elastic fluid through said ducts, aduct chamber disposed at the end of said mill andhavingconcausing movement of elastic fluid through said ducts, and deflector means for deflecting iuid currents entering the mill through said inlet opening away from said outlet opening.

In testimony whereof I hereto aflix my signature.

HARLOWE HARDINGE.

Til

nection with said ducts and with said blower 14. In combination, a rotary grinding mill having outlet and inlet openings at one end, means in said mill for deflecting the elastic fluid current entering the mill away from the` elastic fluid current leaving the mill, station-1 ary inlet and outlet ducts having connection with said inlet and `outlet openings, means for causing the flow of elastic fluid through said ducts and mill, a duct chamber disposed at the end of said mill and having connection with said ducts and with said firstnamed means, a by-pass between `the duct delivering elastic fluid to said mill and the duct chamber, and a damper variably positionable for controlling the amount of elastic fluid flowing .f

from said mill to said duct chamber and for concomitantly controlling the opening of said by-pass.

15. In combination, a grinding mill com.

prising a rotary drum having a grinding compartment comprising a conical feed end and a conical' discharge end, said discharge end having outlet and inlet openings, ducts having connection with said inlet and outlet openingsfor introducing elastic fluid to said mill andfor removing elastic fluid from said mill, one of said ducts being disposed within the other of said ducts, exhauster means for 

